Multi-protocol label switching (MPLS) is a technology utilized to manage traffic over a network. MPLS uses labels that are assigned to a stream of traffic to route the traffic across the network. Each node of the network supports MPLS by reviewing incoming traffic received over the network and forwarding that traffic based on its label.
MPLS networks with traffic engineering capabilities can optimize traffic engineering resource allocation for customized traffic services. In MPLS networks with traffic engineering, the protected label switch path (LSP) is set up for each customized traffic service. A back-up LSP for each customized traffic service is utilized in case of a failure of the protected LSP and must be configured manually. Each of the links in the back-up LSP is manually selected to construct a back-up LSP with a goal of creating a disjointed path that can be relied upon when the protected LSP is in a state of failure.
MPLS and the use of protected LSPs and back-up LSPs can be employed in any network topology. In a ring topology, a protected LSP and back-up LSP are more likely to have a less disjointed path resulting in a greater number of shared links. A failure in a ring topology is likely to create a scenario where traffic being routed from a protected LSP onto a back-up LSP after the failure of a link in the protected LSP passes over links near a point of local repair twice.
The traffic traverses the ring on the protected LSP toward the point of local repair where it is routed onto the back-up LSP. The traffic on the back-up LSP traverses the ring in the opposite direction traversing links near the point of local repair for a second time. Similarly, traffic often passes over links near the merge point twice. As a result these links near the point of local repair and the merge point have their bandwidth requirements doubled in the event of a protection switch from the protected LSP to the back-up LSP. This can cause significant bandwidth issues, especially when this doubling of the bandwidth requirements nears or exceeds the bandwidth of the link.